Incendiary capsule

ABSTRACT

An incendiary capsule has a body forming a single compartment containing a first part of a two part ignition system and a quantity of a pyrotechnic heat source (PHS). The capsule is initiated by injecting, when ready for use, a quantity of a second part of the two part ignition system. The ignition system generates sufficient heat to initiate the PHS, which burns at a substantially higher temperature than the ignition system.

FIELD OF THE INVENTION

The present invention relates to an incendiary capsule particularly,although not exclusively, for use in airborne fire control and forestrymanagement procedures such as back burning.

BACKGROUND OF THE INVENTION

It is known to drop incendiaries from air craft such as helicopters andlight fixed wing aircraft for the purposes of forestry management andback burning. One known incendiary is in the form of a small sphere ofapproximately 32 mm diameter of a plastics material filled with aquantity of potassium permanganate granules or powder. The sphere isinjection moulded from extruded plastic. A small hole is formed in thesphere to allow it to be filled with potassium permanganate. The hole isthen sealed with wax or glue. The spheres are placed in a hopper whichfeeds the sphere sequentially to a chute where they are injected with asmall volume of glycol. The potassium permanganate and glycol reactexothermically generating a flame.

The inventor developed an alternate form of incendiary described in U.S.Pat. No. 6,877,433 in which the incendiary comprises a plurality ofcontainers containing a volume of potassium permanganate which issubsequently injected with a volume of glycol. The containers arecoupled together to form a belt which is fed through a dispensingmachine that sequentially injects the capsules with glycol and separatescapsules from the belt for subsequent dispensing.

SUMMARY OF THE INVENTION

One aspect of the invention provides an incendiary capsule comprising:

-   -   a capsule body;    -   a quantity of a pyrotechnic heat source (PHS) disposed in the        capsule body; and,    -   a quantity of a first part of a two part ignition system        disposed in the capsule body, the first part being reactive with        a second part of the ignition system which when contacted by the        first part in the capsule body causes an exothermic reaction        which generates sufficient heat to ignite the PHS.

The PHS may comprise a liquid impervious coating or covering.

The liquid impervious coating or covering may comprise a liquid whichdries or sets on the PHS to form liquid impervious layer on the PHS.

The liquid impervious covering or coating may comprise an adhesive tapecomprising a layer of adhesive for adhering onto the PHS, the layer ofadhesive provided on a liquid impervious backing strip.

The liquid impervious coating or covering may comprise a coating of aplastics film.

The liquid impervious coating or covering may comprise a container madeof a material that ignites at or below the temperature generated by theexothermic reaction.

The PHS may be provided in the form of a pellet.

The capsule body may comprise has an opening through which the PHS andfirst part of the ignition system are deposited into the capsule, and aseal that extends across and seals the opening.

The capsule body may be made of a plastics material and be provided witha flat bottom wall and a frusto-conical side wall wherein the side wallreduces in diameter from the opening to the bottom wall.

The capsule body may be provided with a lip extending about the openingand lying on a plane substantially parallel to a plane containing thebottom wall.

The seal may comprise a layer of plastics material.

The seal may comprise a layer of transparent or translucent plasticsmaterial.

The PHS may comprise thermite or may be based on a thermite likecomposition.

In one embodiment the PHS comprises by weight:

-   -   40-50% barium nitrate    -   15-20% potassium nitrate    -   10-15% sulphur    -   15-20% aluminium    -   1-5% gum arabic

When the PHS is in the form of a pellet the liquid impervious coatingmay be a water proof coating and may comprise a solvent or a solventmixture. For example in one embodiment the water proof coating comprisesa mixture of shellac and methylated spirits. The PHS pellet can bedipped in a bath of such a mixture and subsequently removed to allowdrying of the mixture on the pellet thereby forming the coating on thepellet. In this example the mixture may comprise between ten to thirtyparts methylated spirits to one part shellac. In another example themixture comprises about twenty parts methylated spirits to one partshellac.

A second aspect of the invention may provide a belt of incendiarycapsules comprising:

-   -   a plurality of capsules according to the first aspect; and,    -   respective couplings between adjacent capsules, the couplings        joining the capsule bodies in a side by side arrangement to form        a belt.

The couplings may be formed integrally with the capsule bodies.

The couplings may be made of the same material as the capsule bodies.

The couplings may be formed with the same thickness as the side walls ofthe capsule bodies.

The first part of the ignition system may comprise potassiumpermanganate.

The second part of the ignition system may comprise glycol.

A third aspect of the invention may provide an incendiary systemcomprising:

-   -   one or more incendiary capsules according to the first aspect or        a belt of incendiary capsules according to the second aspect;        and,    -   a dispensing apparatus comprising a volume of the second part of        the ignition system and a mechanism for injecting a quantity of        the second part of the ignition system into each incendiary        capsule.

The apparatus may inject the volume of the second part of the ignitionsystem through the seal of each incendiary capsule.

The invention also provides a method of producing a burning heat sourceon the ground comprising:

-   -   providing one or more capsules according to the first aspect;    -   carrying the one or more capsules on an aircraft;    -   holding a supply of a second part of the two part ignition        system on the aircraft;    -   flying the aircraft over the ground;    -   while flying the aircraft depositing a quantity of the second        part of the ignition system into one or more selected capsules;        and,    -   dropping the or each selected capsules with the second part of        the ignition system from the aircraft.

In one embodiment the aircraft is flown at height and the first andsecond parts of the ignition system are provided in respectivequantities wherein the or each dropped capsule reaches the group priorto ignition of the PHS.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described by way ofexample only with reference to the accompanying drawings in which:

FIG. 1A is a top view of a belt of the incendiary capsules in accordancewith an embodiment of the present invention;

FIG. 1B is a section view of an incendiary capsule shown in FIG. 1A;

FIG. 2 is a top view of the incendiary capsule belt shown in FIG. 1Ashowing empty incendiary capsules, except for the right most capsule inwhich is disposed a quantity of PHS in the form of a pellet;

FIG. 3 is a side view of the incendiary capsule belt shown in FIG. 1A;

FIG. 4 is a bottom view of the incendiary capsule belt shown in FIG. 1A;

FIG. 5 is a plan view of the PHS pellet shown in FIG. 2;

FIG. 6 is a side view of the PHS pellet shown in FIG. 5.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1A and 1B illustrate an embodiment of an incendiary capsule 10 inaccordance with the present invention. FIG. 1A illustrates a pluralityof incendiary capsules 10 joined together in the side by sidearrangement to form a flexible incendiary capsule belt 12. FIG. 1Bdepicts a section view through an incendiary capsule 10. Each incendiarycapsule 10 comprises a capsule body 14 which contains a quantity of PHS16 and a first part 18 of a two part ignition system. The second part ofthe ignition system (not shown) is injected into a capsule 10 when thecapsule 10 is ready for use, and reacts with the first part 18 to causean exothermic reaction which generates sufficient heat to ignite the PHS16.

In the present embodiment, the first part 18 of the ignition systemcomprises potassium permanganate granules. PHS 16 is provided in theform of a pellet although it is not essential that the PHS be providedin this form. For example the PHS may also be provided in the form ofgranules or powder.

The PHS may comprise thermite or a thermite like compound or isotherwise based on thermite or a thermite like compound.

In general terms, thermite comprises a composition of a metal powder andmetal oxide which deflagrates at extremely high temperatures typicallyin the order of 2,500-3,500° C. The metal powder in the thermite maycomprise one or more of aluminium, magnesium, calcium, titanium, zinc,silicon, or boron. The metal oxide may comprise one or more of boron(III) oxide, silicon (IV) oxide, chromium (III) oxide, magnesium (IV)oxide, iron (III) oxide, iron (II, III) oxide, copper (II) oxide, andlead (II, IV) oxide.

In one example the PHS comprises a compound, by weight of:

-   -   40-50% barium nitrate    -   15-20% potassium nitrate    -   10-15% sulphur    -   15-20% aluminium    -   1-5% gum arabic

The PHS is pressed to form pellets, with the gum arabic acting as abinder.

FIG. 2 illustrates the belt 12 of empty incendiary capsules 10 save forthe right most capsule 10 in which is disposed a PHS pellet 16. The PHSpellet 16 occupies a relatively small volume of the capsule body 14which is, for example less than 25% of the volume. FIGS. 5 and 6 depicta PHS pellet 16. The pellet has a diameter of approximately 11 mm and athickness which reduces from a maximum of about 4 mm along a centralaxis to about 2 mm at its edge.

The PHS 16 is covered or coated with a liquid impervious and morespecifically water proof material. The type of liquid imperviousmaterial used and its form may vary. When the PHS 16 is in the form of apellet, the liquid impervious material may be provided initially as aliquid which is sprayed on the pellet or into which the PHS pellet isdipped, where the liquid subsequently dries or sets to create a liquidimpervious layer or coating on the PHS pellet 16. In an alternate form,the liquid impervious material may be applied as adhesive tape whichsandwiches the pellet 16. The adhesive tape comprising a layer ofadhesive material, that contacts the pellet 16, provided on a liquidimpervious backing strip. Indeed, when the PHS is in the form of apowder or granules, the powder or granules may be wrapped in an adhesivetape. In an alternate form, the covering or coating may be in the formof a thin film of plastics material such as cling wrap used for wrappingof sandwiches and other foodstuffs. This type of covering or coating issuitable for the PHS in pellet, and powder or granule form. In a furtheralternate, the liquid impervious material may be provided as a smallercapsule or container in which the PHS 16, in pellet or powder or granuleform is contained, the container being made of material that ignites ata temperature at or below the temperature generated by the exothermicreaction between the first and second parts of the ignition system. Suchcontainers or small capsules may be in the form for example of capsulesused for medicines.

In one example a water proof coating is provided by dipping pellets 16into a liquid bath of a solvent or solvent mixture and subsequentlyremoved to allow drying of the liquid leaving a water proof coating onthe pellet. A solvent mixture of shellac and methylated spirits has beenfound effective in forming the water proof coating. The mixture is often to thirty parts methylated spirits to one part shellac, with amixture ratio of twenty (20) parts methylated spirits to one partshellac being particularly effective.

Present ignition system comprises potassium permanganate 18, and glycolwhich, when mixed cause an exothermic reaction generating heatsufficient to ignite the thermite. However alternate two part chemicalignition systems may be used provided they generate sufficient heat toignite the PHS. It is believed that the heat required for this is atleast 600-700° C.

The capsule bodies 14 comprise a substantially planar bottom wall 20 anda frusto-conical side wall 22. The side wall 22 decreases in diameter ina direction from an opening 24 of the capsule body 14 toward the bottomwall 20. Once the PHS 16 and first part 18 of the ignition system havebeen deposited into the capsule body 14 through the opening 24, a seal26 is placed across and sealed over the opening 24. The seal 26 istypically in the form of a thin film of plastics material. The materialmay be clear or translucent. Thus each capsule 10 comprises a singlesealed compartment containing one part of the two part ignition systemand a PHS 16. The second part of the two part ignition system iscomplete separate from the capsule 10 and remains remote from thecapsule 10 until it is desired to initiate a capsule.

A circumferential lip 28 is formed about the opening 24 of the capsule10 and lies in a plane substantially parallel to a plane containing thebottom wall 20. The seal 26 is adhered or otherwise attached to the lip28.

In order to form the flexible belt 12, adjacent capsules 10 are joinedby coupling 30. The couplings 30 extend in a plane containing a lip 28.The couplings 30 are formed integrally with and of the same material asthe capsule body 14 and have the same thickness as the side wall 22 andthe lip 28.

In use, the incendiaries 10 may be provided in the form of flexiblebelts 12 wound into reels which may then be fed into a dispenser to forman overall incendiary system. The incendiary system feeds the capsulessequentially to the dispenser which injects a quantity of the secondpart of the ignition system (e.g. glycol) held in a storage vessel ortank into each capsule 10 through the seal 26 and severs or breaks thecoupling 30 to enable separate dispensing of the incendiaries 10. Duringthis process a needle may be used to inject the glycol into the capsules10, where the need is controlled to penetrate into the capsule to adepth that does not reach the PHS 16. The first and second parts of theignition system chemically react to generate heat sufficient tosubsequently cause ignition of the PHS 16. When dispensing theincendiaries 10 from an aircraft, the capsules are dispensed from aheight and contain quantities of the first and second parts of theignition system such that the capsules will reach the ground prior tothe ignition system generating sufficient heat to ignite the PHS 16 sothat the PHS 16 ignites and burns or combusts when the capsule 10reaches the ground.

Modifications and variations to the described embodiments of the presentinvention that would be obvious to a person of ordinary skill in the artare deemed to be within the scope of the present invention the nature ofwhich is to be determined from the above description and the appendedclaims.

1-30. (canceled)
 31. An incendiary capsule comprising: a capsule body; aquantity of a pyrotechnic heat source (PHS) disposed in the capsulebody; and, a quantity of a first part of a two part ignition systemdisposed in the capsule body, the first part being reactive with asecond part of the ignition system which when contacted by the firstpart in the capsule body causes an exothermic reaction which generatessufficient heat to ignite the PHS.
 32. The incendiary capsule accordingto claim 31 wherein the PHS comprises a liquid impervious coating orcovering.
 33. The incendiary capsule according to claim 32 wherein theliquid impervious coating or covering comprises a liquid which dries orsets on the thermite to form liquid impervious layer on the PHS.
 34. Theincendiary capsule according to claim 32 wherein the liquid imperviouscovering or coating comprises an adhesive tape comprising a layer ofadhesive for adhering onto the PHS, the layer of adhesive provided on aliquid impervious backing strip.
 35. The incendiary capsule according toclaim 32 wherein the liquid impervious coating or covering is a coatingof a plastics film.
 36. The incendiary capsule according to claim 32wherein the liquid impervious coating or covering is a container made ofa material that ignites at or below the temperature generated by theexothermic reaction.
 37. An incendiary capsule according to claim 32wherein the PHS is in the form of a pellet.
 38. The incendiary capsuleaccording to claim 37 wherein the PHS comprises thermite.
 39. Theincendiary capsule according to claim 31 wherein the PHS is a compoundcomprising, by weight: 40-50% barium nitrate 15-20% potassium nitrate10-15% sulphur 15-20% aluminium 1-5% gum arabic
 40. The incendiarycapsule according to claim 32 wherein the liquid impervious coatingcomprises a solvent or solvent mixture applied as a liquid on the PHSand subsequently allowed to dry to form the coating.
 41. The incendiarycapsule according to claim 40 wherein the solvent mixture comprises amixture of shellac and methylated spirits.
 42. The incendiary capsuleaccording to claim 31 wherein the capsule body consists of a singlesealed compartment containing the first part of the two part ignitionsystem and the PHS.
 43. The incendiary capsule according to claim 31wherein the capsule body has an opening through which the thermite andfirst part of the ignition system are deposited into the capsule, and aseal that extends across and seals the opening.
 44. A belt of incendiarycapsules comprising: a plurality of capsules according to claim 31; and,respective couplings between adjacent capsules, the couplings joiningthe capsule bodies in a side by side arrangement to form a belt.
 45. Thebelt according to claim 44 wherein the couplings are formed integrallywith the capsule bodies.
 46. The belt according to claim 45 wherein thecouplings are made of the same material as the capsule bodies.
 47. Theincendiary capsules according to claim 32 wherein the first part of theignition system is potassium permanganate.
 48. The incendiary capsulesaccording to claim 47 wherein the second part of the ignition system isglycol.
 49. A method of producing a burning heat source on the groundcomprising: providing one or more capsules according to claim 31;carrying the one or more capsules on an aircraft; holding a supply of asecond part of the two part ignition system on the aircraft; flying theaircraft over the ground; while flying the aircraft depositing aquantity of the second part of the ignition system into one or moreselected capsules; and, dropping the or each selected capsules with thesecond part of the ignition system from the aircraft.
 50. The methodaccording to claim 49 wherein the aircraft is flown at a height and thefirst and second parts of the ignition system are provided in respectivequantities such that the dropped capsules reach the group prior toignition of the PHS.